Recently, in response to demands for the speed up of semiconductor devices, miniaturization and high-integration of wiring patterns, it is required to reduce the capacity between wiring lines and improve conductivity and electromigration resistance of the wiring line. Accordingly, as wiring materials, copper (Cu) having higher conductivity and better electromigration resistance than aluminum (Al) or tungsten (W) of the related art is used. As a technology that forms a Cu wiring line, a damascene method that forms a wiring groove or connecting hole in the interlayer insulating film in advance, and then buries the copper therein is widely used (see, for example, Japanese Patent Application Laid-Open No. 2002-083869).
In the meantime, as the semiconductor devices become miniaturized, a parasitic capacity of the interlayer insulating film has been an important factor for improving the performance of the wiring line and a low permittivity film (low-k film) formed of a low permittivity material is used as the interlayer insulating film. As the material constituting the low-k film, a material having an alkyl group such as a methyl group as a terminal group is generally used.
However, in the damascene process in the related art as above, the low-k film is damaged when performing an etching process or a resist film removing (ashing) process. The damage may cause the increase in a specific permittivity or the leakage current value of the low-k film, which impairs the effect of the usage of the low-k film as the interlayer insulating film.
As a technology that recovers the above-mentioned damage, Japanese Patent Application Laid-Open No. 2006-049798 suggests a method that recovers the damage using a silylating agent such as N-trimethylsilyldimethylamine (TMSDMA) after etching or removing a resist film. This method reforms a surface of the damaged layer whose terminal group is changed to an —OH group due to the damage using a processing gas having a methyl group such as a silylating agent to make the methyl group or a group containing the methyl group as the terminal group.